Is it the same as the T2 where the solenoid connection is routed through the van to the ignition from the battery then back down the van to the solenoid? (Still learning)
If so I suspect there in lies the problem (along with the usual connector issues this time of year)...fit a hot start relay so that the battery connection to the solenoid is fed via the relay contactors nice and short and the ignition switch merely has to throw the relay less current draw...
read the stuff on starting on the technical and nothing sounds like it... excwpt am thinking of looking at the earthing behind the fuses as i do have a water leak around there.
the chattering is more like graunching!! not solenoid more like poor meshing of cogs!!
think the positive comes off the battery straight to the starter solenoid and the 'exciterwire from the ign. switch.
think the battery might be just on it's way out. what are the recommended batteries these days?